If $x=2\cos t-\cos 2t,y=2\sin t-\sin 2t$ then $\frac{dy}{dx}=$

$x=2\cos t-\cos 2t$

$\frac{dx}{dt}=-2.\sin t+\sin 2t\left(2\right)$

$y=2.\sin t-\sin 2t$

$\frac{dy}{dt}=2.\cos t-\cos 2t.\left(2\right)$

$\frac{dy}{dx}=\frac{2[\cos t-\cos 2t]}{2[\sin 2t-\sin t]}$

$=\frac{2\sin \left(\frac{3t}{2}\right).\sin \left(\frac{t}{2}\right)}{2.\cos \left(\frac{3t}{2}\right).\sin \left(\frac{t}{2}\right)}$

$=\cot \left(\frac{3t}{2}\right)$